Method for preparing cha-type molecular sieves using an alkali metal silicate precursor and novel structure directing agents

ABSTRACT

The present invention is directed to a process for preparing CHA-type molecular sieves using a colloidal aluminosilicate composition containing a cationic structure directing agent selected from the group consisting of N-cyclohexyl-N-methylpyrrolidinium, N-cyclohexyl-N-ethylpyrrolidinium, N-methyl-N-(3-methylcyclohexyl)pyrrolidinium, N-ethyl-N-(3-methylcyclohexyl)pyrrolidinium, N-methyl-N-(2-methylcyclohexyl)-pyrrolidinium, N-ethyl-N-(2-methylcyclohexyl)pyrrolidinium, and mixtures thereof.

FIELD OF THE INVENTION

The present invention is directed to a process for preparing CHA-typemolecular sieves using an alkali metal silicate and a cationic structuredirecting agent selected from the group consisting ofN-cyclohexyl-N-methylpyrrolidinium, N-cyclohexyl-N-ethylpyrrolidinium,N-methyl-N-(3-methylcyclohexyl)pyrrolidinium,N-ethyl-N-(3-methylcyclohexyl)pyrrolidinium,N-methyl-N-(2-methylcyclohexyl)pyrrolidinium,N-ethyl-N-(2-methylcyclohexyl)pyrrolidinium cations, and mixturesthereof.

BACKGROUND OF THE INVENTION

Molecular sieves are a commercially important class of crystallinematerials. They have distinct crystal structures with ordered porestructures which are demonstrated by distinct X-ray diffractionpatterns. The crystal structure defines cavities and pores which arecharacteristic of the different species.

Molecular sieves identified by the International Zeolite Associate (IZA)as having the structure code CHA are known. For example, the molecularsieve known as SSZ-13 is a known crystalline CHA material. It isdisclosed in U.S. Pat. No. 4,544,538, issued Oct. 1, 1985 to Zones. Inthat patent, the SSZ-13 molecular sieve is prepared in the presence of aN-alkyl-3-quinuclidinol cation, a N,N,N-trialkyl-1-adamantammoniumcation and/or, and N,N,N-trialkyl-2-exoaminonorbornane cation as thestructure-directing agent (SDA).

U.S. Publication No. 2007-0286798 to Cao et al., published Dec. 13,2007, discloses the preparation of CHA-type molecular sieves usingvarious SDAs, including a N,N,N-trimethyl-2-adamantammonium cation.

However, SDAs useful for making CHA materials are complex and typicallynot available in quantities necessary to produce CHA materials on acommercial scale. In addition, there is a continuous need to reduce theconcentration of known CHA SDAs in the reaction mixture to an absoluteminimum, or replace them entirely with SDAs that are cheaper, lesscomplex and/or reduce the time necessary to form product.

It has now been found that CHA-type molecular sieves can be preparedusing an alkali metal silicate and at least one of the novel structuredirecting agents described herein below.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a method ofpreparing CHA-type molecular sieves by contacting under crystallizationconditions (1) an alkali metal silicate; (2) one or more sources of oneor more oxides selected from the group consisting of oxides of trivalentelements, pentavalent elements, and mixtures thereof; (3) at least onesource of an element selected from Groups 1 and 2 of the Periodic Table;(4) at least one structure directing agent selected from the groupconsisting of cations represented by structures (1) through (6) below;and (5) hydroxide ions.

The present invention also includes a process for preparing a CHA-typemolecular sieve by:

(a) preparing a reaction mixture containing (1) an alkali metalsilicate; (2) one or more sources of one or more oxides selected fromthe group consisting of oxides of trivalent elements, pentavalentelements, and mixtures thereof; (3) at least one source of an elementselected from Groups 1 and 2 of the Periodic Table; (4) at least onestructure directing agent selected from the group consisting of cationsrepresented by structures (1) through (6) below; (5) hydroxide ions; and(6) water; and

(b) subjecting the reaction mixture to crystallization conditionssufficient to form crystals of the CHA-type molecular sieve.

Where the molecular sieve formed is an intermediate material, theprocess of the present invention includes a further post-crystallizationprocessing in order to achieve the target molecular sieve (e.g. bypost-synthesis heteroatom lattice substitution or acid leaching).

The present invention also provides a CHA-type molecular sieve having acomposition, as-synthesized and in the anhydrous state, in terms of moleratios, as follows:

Broadest Secondary SiO₂/X₂O_(a)  10-300  20-100 Q/SiO₂ 0.05-0.4 0.1-0.2M/SiO₂ 0.01-1   0.2-0.6wherein:

(1) X is selected from the group consisting of trivalent and pentavalentelements from Groups 3-13 of the Periodic Table, and mixtures thereof;

(2) stoichiometric variable a equals the valence state of compositionalvariable X (e.g. when X is trivalent, a=3; when X is pentavalent, a=5);

(3) M is selected from the group consisting of elements from Groups 1and 2 of the Periodic Table; and

(4) Q is one of the novel structure directing agents represented bystructures (1) through (6) below

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a powder x-ray diffraction (XRD) pattern of the as-mademolecular sieve prepared according to Example 10 of the presentinvention.

FIG. 2 shows a powder XRD pattern of the calcined molecular sieveprepared according to Example 10 of the present invention.

FIG. 3 shows a powder XRD pattern of the as-made molecular sieveprepared according to Example 11 of the present invention.

FIG. 4 shows a powder XRD pattern of the calcined molecular sieveprepared according to Example 11 of the present invention.

FIG. 5 shows a powder XRD pattern of the as-made molecular sieveprepared according to Example 12 of the present invention.

FIG. 6 shows a powder XRD pattern of the calcined molecular sieveprepared according to Example 12 of the present invention.

FIG. 7 shows a powder XRD pattern of the as-made molecular sieveprepared according to Example 13 of the present invention.

FIG. 8 shows a powder XRD pattern of the calcined molecular sieveprepared according to Example 13 of the present invention.

FIG. 9 shows a powder XRD pattern of the as-made molecular sieveprepared according to Example 14 of the present invention.

FIG. 10 shows a powder XRD pattern of the calcined molecular sieveprepared according to Example 14 of the present invention.

FIG. 11 shows a powder XRD pattern of the as-made molecular sieveprepared according to Example 15 of the present invention.

FIG. 12 shows a powder XRD pattern of the calcined molecular sieveprepared according to Example 15 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Introduction

The term “Periodic Table” refers to the version of IUPAC Periodic Tableof the Elements dated Jun. 22, 2007, and the numbering scheme for thePeriodic Table Groups is as described in Chemical and Engineering News,63(5), 27 (1985).

The term “molecular sieve” includes (a) intermediate and (b) final ortarget molecular sieves and zeolites produced by (1) direct synthesis or(2) post-crystallization treatment (secondary synthesis). Secondarysynthesis techniques allow for the synthesis of a target material froman intermediate material by heteroatom lattice substitution or othertechniques. For example, an aluminosilicate can be synthesized from anintermediate borosilicate by post-crystallization heteroatom latticesubstitution of the Al for B. Such techniques are known, for example asdescribed in U.S. Pat. No. 6,790,433 to C. Y. Chen and Stacey Zones,issued Sep. 14, 2004.

The term “CHA-type molecular sieve” includes all molecular sieves andtheir isotypes that have been assigned the International ZeoliteAssociate framework code CHA, as described in the Atlas of ZeoliteFramework Types, eds. Ch. Baerlocher, L. B. McCusker and D. H. Olson,Elsevier, 6^(th) revised edition, 2007. The Atlas of Zeolite FrameworkTypes classes several differently named materials as having this sameCHA topology, including SSZ-13 and SSZ-62.

It will be understood by a person skilled in the art that the CHA-typemolecular sieve materials made according to the process described hereinmay contain impurities, such as amorphous materials; unit cells havingnon-CHA framework topologies (e.g., MFI, MTW, MOR, Beta); and/or otherimpurities (e.g., heavy metals and/or organic hydrocarbons).

Where permitted, all publications, patents and patent applications citedin this application are herein incorporated by reference in theirentirety; to the extent such disclosure is not inconsistent with thepresent invention.

Unless otherwise specified, the recitation of a genus of elements,materials or other components, from which an individual component ormixture of components can be selected, is intended to include allpossible sub-generic combinations of the listed components and mixturesthereof. Also, “include” and its variants are intended to benon-limiting, such that recitation of items in a list is not to theexclusion of other like items that may also be useful in the materials,compositions and methods of this invention.

The present invention is directed to a method of making CHA-typemolecular sieves using an alkali metal silicate and a structuredirecting agent (SDA) selected from the group consisting of cationsrepresented by structures (1) through (6), and mixtures thereof:

Reaction Mixture

In general, the CHA-type molecular sieve is prepared by:

(a) preparing a reaction mixture containing (1) an alkali metalsilicate; (2) one or more sources of one or more oxides selected fromthe group consisting of oxides of trivalent elements, pentavalentelements, and mixtures thereof; (3) at least one source of an elementselected from Groups 1 and 2 of the Periodic Table; (4) at least onestructure directing agent selected from the group consisting of cationsrepresented by structures (1) through (6) herein; (5) hydroxide ions;and (6) water; and

(b) subjecting the reaction mixture to crystallization conditionssufficient to form crystals of the CHA-type molecular sieve.

Where the molecular sieve formed is an intermediate material, theprocess of the present invention includes a further step of synthesizinga target molecular sieve by post-synthesis techniques, such asheteroatom lattice substitution techniques and acid leaching.

The composition of the reaction mixture from which the CHA-typemolecular sieve is formed, in terms of molar ratios, is identified inTable 1 below:

TABLE 1 Reactants Broad Subembodiment SiO₂/X₂O_(a) molar ratio  10-300 20-100 M/SiO₂ molar ratio 0.01-1   0.2-0.6 Q/SiO₂ molar ratio 0.05-0.4 0.1-0.3 OH⁻/SiO₂ molar ratio 0.1-1.0 0.2-0.7 H₂O/SiO₂ molar ratio 10-5025-40wherein compositional variables X, M, Q and a are as described hereinabove.

The processes for making CHA-type molecular sieve described hereinemploy an alkali metal silicate as the SiO₂ source. Examples of analkali metal silicate useful for making CHA-type molecular sieves usingthe structure directing agents described herein include sodium silicateand potassium silicate.

For each embodiment described herein, X is selected from the groupconsisting of elements from Groups 3-13 of the Periodic Table. In onesubembodiment, X is selected from the group consisting of gallium (Ga),aluminum (Al), iron (Fe), boron (B), indium (In), and mixtures thereof.In another subembodiment, X is selected from the group consisting of Al,B, Fe, Ga, and mixtures thereof. In another subembodiment, X is selectedfrom the group consisting of Al, Fe, Ga, and mixtures thereof. Sourcesof elements selected for optional composition variable X include oxides,hydroxides, acetates, oxalates, ammonium salts and sulfates of theelement(s) selected for X. Typical sources of aluminum oxide includealuminates, alumina, and aluminum compounds such as AlCl₃, Al₂(SO₄)₃,aluminum hydroxide (Al(OH₃)), kaolin clays, and other zeolites. Anexample of the source of aluminum oxide is LZ-210, NH₄-Y62 zeolite, andNa-Y52 zeolite (various versions of Y zeolite). Boron, gallium, and ironcan be added in forms corresponding to their aluminum and siliconcounterparts.

As described herein above, for each embodiment described herein, thereaction mixture may be formed using at least one source of an elementselected from Groups 1 and 2 of the Periodic Table (referred to hereinas M). In one subembodiment, the reaction mixture is formed using asource of an element from Group 1 of the Periodic Table. In anothersubembodiment, the reaction mixture is formed using a source of sodium(Na). Any M-containing compound which is not detrimental to thecrystallization process is suitable. Sources for such Groups 1 and 2elements include oxides, hydroxides, nitrates, sulfates, halides,oxalates, citrates and acetates thereof.

The SDA cation is typically associated with anions (X⁻) which may be anyanion that is not detrimental to the formation of the zeolite.Representative anions include elements from Group 17 of the PeriodicTable (e.g., fluoride, chloride, bromide and iodide), hydroxide,acetate, sulfate, tetrafluoroborate, carboxylate, and the like.

The reaction mixture can be prepared either batch wise or continuously.Crystal size, morphology and crystallization time of the molecular sievedescribed herein may vary with the nature of the reaction mixture andthe crystallization conditions.

Crystallization and Post-Synthesis Treatment

In practice, the molecular sieve is prepared by:

(a) preparing a reaction mixture as described herein above; and

(b) maintaining the reaction mixture under crystallization conditionssufficient to form the molecular sieve. (See, Harry Robson, VerifiedSyntheses of Zeolitic Materials, 2^(nd) revised edition, Elsevier,Amsterdam (2001)).

The reaction mixture is maintained at an elevated temperature until themolecular sieve is formed. The hydrothermal crystallization is usuallyconducted under pressure, and usually in an autoclave so that thereaction mixture is subject to autogenous pressure, at a temperaturebetween 130° C. and 200° C., for a period of one to six days.

The reaction mixture may be subjected to mild stirring or agitationduring the crystallization step. It will be understood by a personskilled in the art that the molecular sieves described herein maycontain impurities, such as amorphous materials, unit cells havingframework topologies which do not coincide with the molecular sieve,and/or other impurities (e.g., organic hydrocarbons).

During the hydrothermal crystallization step, the molecular sievecrystals can be allowed to nucleate spontaneously from the reactionmixture. The use of crystals of the molecular sieve as seed material canbe advantageous in decreasing the time necessary for completecrystallization to occur. In addition, seeding can lead to an increasedpurity of the product obtained by promoting the nucleation and/orformation of the molecular sieve over any undesired phases. When used asseeds, seed crystals are added in an amount between 1% and 10% of theweight of the source for compositional variable T used in the reactionmixture.

Once the molecular sieve crystals have formed, the solid product isseparated from the reaction mixture by standard mechanical separationtechniques such as filtration. The crystals are water-washed and thendried to obtain the as-synthesized molecular sieve crystals. The dryingstep can be performed at atmospheric pressure or under vacuum.

The molecular sieve can be used as-synthesized, but typically will bethermally treated (calcined). The term “as-synthesized” refers to themolecular sieve in its form after crystallization, prior to removal ofthe SDA. The SDA can be removed by thermal treatment (e.g.,calcination), preferably in an oxidative atmosphere (e.g., air, gas withan oxygen partial pressure of greater than 0 kPa) at a temperaturereadily determinable by one skilled in the art sufficient to remove theSDA from the molecular sieve. The SDA can also be removed by photolysistechniques (e.g. exposing the SDA-containing molecular sieve product tolight or electromagnetic radiation that has a wavelength shorter thanvisible light under conditions sufficient to selectively remove theorganic compound from the molecular sieve) as described in U.S. Pat. No.6,960,327 to Navrotsky and Parikh, issued Nov. 1, 2005.

The molecular sieve can subsequently be calcined in steam, air or inertgas at temperatures ranging from about 200° C. to about 800° C. forperiods of time ranging from 1 to 48 hours, or more. Usually, it isdesirable to remove the extra-framework cation (e.g. H⁺) by ion-exchangeor other known method and replace it with hydrogen, ammonium, or anydesired metal-ion.

Where the molecular sieve formed is an intermediate material, the targetmolecular sieve can be achieved using post-synthesis techniques such asheteroatom lattice substitution techniques. The target molecular sieve(e.g. silicate SSZ-13) can also be achieved by removing heteroatoms fromthe lattice by known techniques such as acid leaching.

The molecular sieve made from the process of the present invention canbe formed into a wide variety of physical shapes. Generally speaking,the molecular sieve can be in the form of a powder, a granule, or amolded product, such as extrudate having a particle size sufficient topass through a 2-mesh (Tyler) screen and be retained on a 400-mesh(Tyler) screen. In cases where the catalyst is molded, such as byextrusion with an organic binder, the molecular sieve can be extrudedbefore drying, or, dried or partially dried and then extruded.

The molecular sieve can be composited with other materials resistant tothe temperatures and other conditions employed in organic conversionprocesses. Such matrix materials include active and inactive materialsand synthetic or naturally occurring zeolites as well as inorganicmaterials such as clays, silica and metal oxides. Examples of suchmaterials and the manner in which they can be used are disclosed in U.S.Pat. No. 4,910,006, issued May 20, 1990 to Zones et al., and U.S. Pat.No. 5,316,753, issued May 31, 1994 to Nakagawa.

Characterization of the Molecular Sieve

The CHA molecular sieves made by the process of the present inventionhave a composition, as-synthesized and in the anhydrous state, asdescribed in Table 2 (in terms of mole ratios):

TABLE 2 Broadest Secondary SiO₂/X₂O_(a)  10-300  20-100 Q/SiO₂ 0.05-0.40.1-0.2 M/SiO₂ 0.01-1   0.2-0.6wherein compositional variables X, M, Q and a are as described hereinabove.

The CHA-type molecular sieves synthesized by the process of the presentinvention are characterized by their X-ray diffraction pattern (XRD).X-ray diffraction patterns representative of CHA-type molecular sievescan be referenced in M. M. J. Treacy et al., Collection of Simulated XRDPowder Patterns for Zeolites, 5th Revised Edition, 2007 of theInternational Zeolite Association. Minor variations in the diffractionpattern can result from variations in the mole ratios of the frameworkspecies of the particular sample due to changes in lattice constants. Inaddition, sufficiently small crystals will affect the shape andintensity of peaks, leading to significant peak broadening. Minorvariations in the diffraction pattern can also result from variations inthe organic compound used in the preparation and from variations in theSi/AI mole ratio from sample to sample. Calcination can also cause minorshifts in the X-ray diffraction pattern. Notwithstanding these minorperturbations, the basic crystal lattice structure remains unchanged.

The powder X-ray diffraction patterns presented herein were collected bystandard techniques. The radiation was CuK-α radiation. The peak heightsand the positions, as a function of 2θ where θ is the Bragg angle, wereread from the relative intensities of the peaks, and d, the interplanarspacing in Angstroms corresponding to the recorded lines, can becalculated.

EXAMPLES

The following examples demonstrate but do not limit the presentinvention.

Example 1 Synthesis of Cyclohexylpyrrolidine

Cyclohexylpyrrolidine was prepared as described in the procedure below.In a 3-neck reaction flask equipped with a mechanical stirrer andheating mantle, a 2 molar equivalent of pyrrolidine were mixed with 1molar equivalent of cyclohexanone in dry cyclohexane to make a 1Msolution with respect to the cyclohexanone. To the mixture, 2 molarequivalents of anhydrous MgSO₄ (as dehydrating agent) were added. Theresulting mixture was refluxed for 94 hours. The progress of thereaction was monitored by NMR analysis.

After heating for 96 hours, the reaction was completed and reactionmixture was cooled down, filtered and concentrated on a rotaryevaporator to remove excess pyrrolidine and cyclohexanone. The obtainedoil was dissolved in cyclohexane and hydrogenated at 60 psi hydrogenpressure in the presence of 10% palladium on activated carbon (10 mol %with respect the produced cyclohexenylpyrrolidine) on a hydrogenationParr. The reaction was left to gently shake overnight. Oncehydrogenation is complete, the reaction mixture was filtered through afritted glass funnel and the filtrate was concentrated on a rotaryevaporator to remove the solvent (cyclohexane). The desiredcyclohexanylpyrrolidine was obtained in 91% yield as colorless oil.

In some instances when some unreacted cyclohexanone is still in thereaction mixture, the product after hydrogenation was purified by adding3M HCl solution to the mixture (after filtering out the palladium/carboncatalyst) and left to stir for 15-20 minutes. The resulting mixture isthen extracted with diethyl ether to remove the cyclohexanone from themixture and leaving behind the cyclohexylpyrrolidinium hydrochloridesalt. The water layer containing cyclohexylpyrrolidinium hydrochloridesalt is separated and then neutralized with NaOH solution to a pH of9-10. The free cyclohexylpyrrolidine is extracted with ethyl acetate,dried over MgSO₄ and concentrated on a rotary evaporator at reducedpressure to give the desired product free from any impurities.

Example 2 Synthesis of N-(3-methylcyclohexyl)pyrrolidine

N-(3-methylcyclohexyl)pyrrolidine was synthesized using the proceduredescribed in example 1 above using 3-methylcyclohexanone in place ofcyclohexanone.

The condensation reaction yields an isomeric mixture ofN-(3-methylcyclohex-1-enyl)pyrrolidine andN-(5-methylcyclohex-1-enyl)pyrrolidine which upon hydrogenation yieldedthe desired a N-(3-methylcyclohexyl)pyrrolidine in 88% yield ascolorless oil.

Example 3 Synthesis of N-(2-methylcyclohexyl)pyrrolidine

Using the same procedure describes in example 1 above,N-(2-methylcyclohexyl)pyrrolidine was synthesized by replacingcyclohexanone with 2-methylcyclohexanone. The condensation reactionyielded an mixture of N-(2-methylcyclohexyl-1-enyl)pyrrolidine andN-(6-methylcyclohex-1-enyl)pyrrolidine which upon hydrogenation yieldedthe desired N-(2-methylcyclohexyl)pyrrolidine in 85% as colorless oil.

Example 4 Synthesis of N-Methyl-N-Cyclohexylpyrrolidinium Hydroxide

N-cyclohexylpyrrolidine prepared in Example 1 (1 molar equivalent) wasdissolved in methanol to 0.5M concentration in a three neck reactionflask equipped with a mechanical stirrer and reflux condenser. To themethanolic solution of cyclohexylpyrrolidine, 2 molar equivalents ofmethyl iodide were added, and the resulting mixture was left to stirovernight. The mixture was heated to reflux and left to stir at refluxfor 4 hours. The reaction was cooled down and left to stir overnight.The reaction was complete. The reaction mixture was concentrated on arotary evaporator. The resulting tan-colored solids were dissolved inisopropyl alcohol and then precipitated out from solution by addingdiethyl ether. The precipitate was filtered out and dried on a rotaryevaporator at reduced pressure and in hot water bath at 80° C. to givethe desired N-methyl-N-cyclohexylpyrrolidinium iodide in 86% yield.N-Methyl-N-cyclohexylpyrrolidinium iodide was converted to the hydroxideby ion-exchanging the iodide ion with hydroxide ion. In a polyethyleneplastic bottle, N-methyl-N-cyclohexylpyrrolidinium iodide salt wasdissolved in deionized water (1 mmol salt/10 ml H₂O). Then Bio-Rad AG1-X8 resin (1.1 g resin/mmol salt) was added and the slurry-like mixturewas gently stirred overnight. The exchange solution was then filteredand a small aliquot was titrated with 0.1N HCl to give 92% yield of theN-methyl-N-cyclohexylpyrrolidinium hydroxide.

Example 5 Synthesis of N-Ethyl-N-Cyclohexylpyrrolidinium Hydroxide

N-cyclohexylpyrrolidine prepared in example 1 was quaternized with ethyliodide according to the procedure describe in example 4 (using ethyliodide in place of methyl iodide). The reaction affordedN-Ethyl-N-cyclohexylpyrrolidinium iodide in 86% yield. The iodide saltwas exchanged with Bio-Rad AG 1-X8 ion-exchange resin as described inexample 4 for the N-methyl-N-cyclohexylpyrrolidinium iodide. Theexchange procedure afforded N-ethyl-N-cyclohexylpyrrolidinium hydroxidein 89% yield (titration analysis).

Example 6 Synthesis of N-Methyl-N-(3-methylcyclohexyl)pyrrolidiniumHydroxide

N-(3-methylcyclohexyl)pyrrolidine prepared in example 2 above wasquaternized with methyl iodide in a similar fashion to the proceduredescribed in example 4. The quaternization afforded the desiredN-methyl-N-(3-methylcyclohexyl)pyrrolidinium iodide in 94% yield. Theresulting iodide salt was exchanged with Bio-Rad AG 1-X8 ion-exchangeresin as described in example 4 to giveN-methyl-N-(3-methylcyclohexyl)pyrrolidinium hydroxide in 98% yield(titration analysis).

Example 7 Synthesis of N-Ethyl-N-(3-methylcyclohexyl)pyrrolidiniumHydroxide

N-(3-methylcyclohexyl)pyrrolidine prepared in example 2 above wasquaternized with ethyl iodide in a similar fashion to the proceduredescribed in example 6 with the exception of using ethyl iodide in placeof methyl iodide. The quaternization afforded the desiredN-ethyl-N-(3-methylcyclohexyl)pyrrolidinium iodide in 85% yield. Theresulting N-ethyl-N-(3-methylcyclohexyl)pyrrolidinium iodide salt wasexchanged with Bio-Rad AG 1-X8 ion-exchange resin as described inexample 4 to give N-methyl-N-(3-methylcyclohexyl)pyrrolidinium hydroxidein 88% yield (by titration).

Example 8 Synthesis of N-methyl-N-(2-methylcyclohexyl)pyrrolidiniumhydroxide

N-(2-methylcyclohexyl)pyrrolidine as synthesized in Example 3 above, wasquaternized with methyl iodide using the procedure described in example4 with the exception of using N-(2-methylcyclohexyl)pyrrolidine in placeof N-cyclohexylpyrrolidine. The quaternization procedure afforded thedesired N-methyl-N-(2-methylcyclohexyl)pyrrolidinium iodide in 94% yieldas an off-white solid. This N-methyl-N-(2-methylcyclohexyl)pyrrolidiniumiodide was ion-exchanged with BIO-RAD AGR 1-X* resin as described inexample 4 above. The ion-exchange procedure afforded the hydroxidesolution of N-methyl-N-(2-methylcyclohexyl)pyrrolidinium cation in 91%yield as determined by titration analysis on a small aliquot.

Example 9 Synthesis of N-Ethyl-N-(2-methylcyclohexyl)pyrrolidiniumHydroxide

Using the same procedure described in examples 4 and 9 above,N-(2-methylcyclohexyl)pyrrolidine was quaternized with ethyl iodide togive N-ethyl-N-(2-methylcyclohexyl)pyrrolidinium iodide whichion-exchanged with hydroxide ion using the aforementioned exchangeprocedures to give the hydroxide solution of theN-ethyl-N-(2-methylcyclohexyl)pyrrolidinium in a combined yield 86% forboth the quaternization and the exchange.

Example 10 Synthesis of Al-SSZ-13 (Al-CHA)

In a 23 CC Teflon liner, 3.6 g of 0.63M ofN-cyclohexyl-N-methylpyrrolidinium hydroxide solution (2 mmol SDA), 0.2g of 1N NaOH solution, 2.7 g sodium silicate, and 0.26 g NH₄—Y (Y-62)zeolite were all mixed and thoroughly stirred until a homogenous mixturewas obtained. The Teflon liner containing the mixture was capped andsealed in a Parr autoclave and heated in an oven at 150° C. whilerotating at ˜43 rpm. The crystallization progress was followed byScanning Electron Microscopy analysis and by monitoring the pH of thereaction solution. The reaction was completed after heating for 6 daysto give a clear solution and a fine powder precipitate with a pH of12.6. The reaction solution was filtered using a fritted glass funnel.The obtained solids were thoroughly rinsed with deionized water (1liter) and were air-dried overnight. Then, the solids were further driedin an oven at 125° C. for 2 hr. The reaction yielded 0.53 g of SSZ-13(CHA) and Mordenite (MOR) zeolites. The reaction usually leads to equalamounts of the two phases and occasionally CHA is produced as thedominant phase. The reaction product was analyzed by powder XRD, and theresulting XRD pattern for the as-made product is shown in FIG. 1.

The as-made product was calcined in air in a muffle furnace oven fromroom temperature to 120° C. at a rate of 1° C./minute and held at 120°C. for 2 hours. The temperature was then ramped up to 540° C. at a rateof 1° C./minute. The sample was held at 540° C. for 5 hrs. Thetemperature was increased at the same rate (1° C./min) to 595° C. andheld there for 5 hrs. The resulting XRD pattern for the calcined productis shown in FIG. 2.

Example 11

Example 10 was repeated but 4.6 g of 0.45M ofN-ethyl-N-cyclohexylpyrrolidinium hydroxide solution was used instead ofN-methyl-N-cyclohexylpyrrolidinium hydroxide solution. The reaction wascomplete in 6 days to give 0.51 g of CHA (SSZ-13) with occasional traceamount of MOR (Mordenite) impurity.

The reaction product was analyzed by powder XRD, and the resulting XRDpattern for the as-made product is shown in FIG. 3. The as-made productwas calcined per the technique described in Example 10 and analyzed bypowder XRD. The resulting XRD pattern for the calcined product is shownin FIG. 4.

Example 12

Example 10 was repeated but N-methyl-N-cyclohexylpyrrolidinium hydroxidewas replaced with 3.3 g of 0.69M ofN-methyl-N-(3-methylcyclohexyl)pyrrolidinium hydroxide solution. Thereaction was done in 6 days and yielded 0.54 g of a mixture of mostlyCHA and little amount of MOR.

The reaction product was analyzed by powder XRD, and the resulting XRDpattern for the as-made product is shown in FIG. 5. The as-made productwas calcined per the technique described in Example 10 and analyzed bypowder XRD. The resulting XRD pattern for the calcined product is shownin FIG. 6.

Example 13

Example 12 was repeated with 3.3 g of 0.68 molar solution ofN-ethyl-N-(3-methylcyclohexyl)pyrrolidinium hydroxide as the SDA. Thereaction was complete in 6 days and provided 0.52 g of CHA with traceamount of MOR (Mordenite).

The reaction product was analyzed by powder XRD, and the resulting XRDpattern for the as-made product is shown in FIG. 7. The as-made productwas calcined per the technique described in Example 10 and analyzed bypowder XRD. The resulting XRD pattern for the calcined product is shownin FIG. 8.

Example 14

Example 10 was repeated but a 3.1 gm of 0.64M solution ofN-methyl-N-(2-methylcyclohexyl)pyrrolidinium hydroxide in placeN-methyl-N-cyclohexylpyrrolidinium hydroxide. The reaction heated for 6days to give 0.48 g of both CHA and MOR in about equal amounts.

The reaction product was analyzed by powder XRD, and the resulting XRDpattern for the as-made product is shown in FIG. 9. The as-made productwas calcined per the technique described in Example 10 and analyzed bypowder XRD. The resulting XRD pattern for the calcined product is shownin FIG. 10.

Example 15

Example 14 was repeated but a 3.3 gm of 0.62M solution ofN-ethyl-N-(2-methylcyclohexyl)pyrrolidinium hydroxide in placeN-methyl-N-cyclohexylpyrrolidinium hydroxide. The reaction heated for 6days to give 0.50 g of mostly CHA and little MOR.

The reaction product was analyzed by powder XRD, and the resulting XRDpattern for the as-made product is shown in FIG. 11. The as-made productwas calcined per the technique described in Example 10 and analyzed bypowder XRD. The resulting XRD pattern for the calcined product is shownin FIG. 12.

What is claimed is:
 1. A method of preparing a CHA-type molecular sieve,comprising: (a) preparing a reaction mixture containing: (1) an alkalimetal silicate; (2) one or more sources of one or more oxides selectedfrom the group consisting of oxides of trivalent elements, pentavalentelements, and mixtures thereof; (3) a cationic structure directing agentselected from the group consisting ofN-cyclohexyl-N-methylpyrrolidinium, N-cyclohexyl-N-ethylpyrrolidinium,N-methyl-N-(3-methylcyclohexyl)pyrrolidinium,N-ethyl-N-(3-methylcyclohexyl)pyrrolidinium,N-methyl-N-(2-methylcyclohexyl)pyrrolidinium,N-ethyl-N-(2-methylcyclohexyl)pyrrolidinium, and mixtures thereof; (4)at least one source of an element selected from Groups 1 and 2 of thePeriodic Table; (5) hydroxide ions; and (6) water; and (b) subjectingthe reaction mixture to crystallization conditions sufficient to formcrystals of the CHA-type molecular sieve.
 2. The method of claim 1,wherein X is selected from the group consisting of Ga, aluminum Al, Fe,B, In, and mixtures thereof.
 3. The method of claim 1, wherein themolecular sieve is prepared from a reaction mixture comprising, in termsof mole ratios, the following: SiO₂/X₂O_(a)  10-300 M/SiO₂ 0.01-1  Q/SiO₂ 0.05-0.4  OH⁻/SiO₂ 0.1-1.0 H₂O/SiO₂ 10-50

wherein: (1) X is selected from the group consisting of trivalent andpentavalent elements from Groups 3-13 of the Periodic Table, andmixtures thereof; (2) stoichiometric variable a equals the valence stateof compositional variable X (e.g. when X is trivalent, a=3; when X ispentavalent, a=5); (3) M is selected from the group consisting ofelements from Groups 1 and 2 of the Periodic Table; and (4) Q is thecationic structure directing agent.
 4. The method of claim 3, whereinthe molecular sieve has a composition comprising, in terms of moleratios, the following: SiO₂/X₂O_(a)  10-300 Q/SiO₂ 0.05-0.4 M/SiO₂0.01-1  


5. The method of claim 4, wherein X is selected from the groupconsisting of Ga, aluminum Al, Fe, B, In, and mixtures thereof.
 6. Themethod of claim 3, wherein X is selected from the group consisting ofGa, aluminum Al, Fe, B, In, and mixtures thereof.
 7. The method of claim3, wherein the molecular sieve has a composition comprising, in terms ofmole ratios, the following: SiO₂/X₂O_(a)  20-100 Q/SiO₂ 0.1-0.2 M/SiO₂0.2-0.6


8. The method of claim 1, wherein the molecular sieve is prepared from areaction mixture comprising, in terms of mole ratios, the following:SiO₂/X₂O_(a)  20-100 M/SiO₂ 0.2-0.6 Q/SiO₂ 0.1-0.3 OH⁻/SiO₂ 0.2-0.7H₂O/SiO₂ 25-40

wherein: (1) X is selected from the group consisting of trivalent andpentavalent elements from Groups 3-13 of the Periodic Table, andmixtures thereof; (2) stoichiometric variable a equals the valence stateof compositional variable X (e.g. when X is trivalent, a=3; when X ispentavalent, a=5); (3) M is selected from the group consisting ofelements from Groups 1 and 2 of the Periodic Table; and (4) Q is thecationic structure directing agent.
 9. The method of claim 8, whereinthe molecular sieve has a composition comprising, in terms of moleratios, the following: SiO₂/X₂O_(a)  10-300 Q/SiO₂ 0.05-0.4 M/SiO₂0.01-1  


10. The method of claim 9, wherein X is selected from the groupconsisting of Ga, aluminum Al, Fe, B, In, and mixtures thereof.
 11. Themethod of claim 7, wherein X is selected from the group consisting ofGa, aluminum Al, Fe, B, In, and mixtures thereof.
 12. The method ofclaim 7, wherein the molecular sieve has a composition comprising, interms of mole ratios, the following: SiO₂/X₂O_(a)  20-100 Q/SiO₂ 0.1-0.2M/SiO₂ 0.2-0.6


13. The method of claim 1, wherein the molecular sieve has acomposition, as made and in the anhydrous state, comprising, in terms ofmole ratios, the following: SiO₂/X₂O_(a)  10-300 Q/SiO₂ 0.05-0.4 M/SiO₂0.01-1  

wherein: (1) X is selected from the group consisting of trivalent andpentavalent elements from Groups 3-13 of the Periodic Table, andmixtures thereof; (2) stoichiometric variable a equals the valence stateof compositional variable X (e.g. when X is trivalent, a=3; when X ispentavalent, a=5); (3) M is selected from the group consisting ofelements from Groups 1 and 2 of the Periodic Table; and (4) Q is thecationic structure directing agent.
 14. The method of claim 13, whereinX is selected from the group consisting of Ga, aluminum Al, Fe, B, In,and mixtures thereof.
 15. The method of claim 1, wherein the molecularsieve has a composition comprising, in terms of mole ratios, thefollowing: SiO₂/X₂O_(a)  20-100 Q/SiO₂ 0.1-0.2 M/SiO₂ 0.2-0.6

wherein: (1) X is selected from the group consisting of trivalent andpentavalent elements from Groups 3-13 of the Periodic Table, andmixtures thereof; (2) stoichiometric variable a equals the valence stateof compositional variable X (e.g. when X is trivalent, a=3; when X ispentavalent, a=5); (3) M is selected from the group consisting ofelements from Groups 1 and 2 of the Periodic Table; and (4) Q is thecationic structure directing agent.
 16. The method of claim 15, whereinX is selected from the group consisting of Ga, aluminum Al, Fe, B, In,and mixtures thereof.
 17. The method of claim 1, wherein the reactionmixture further comprises CHA seed crystals.
 18. The method of claim 1,wherein the alkali metal silicate is sodium silicate.